In an image forming system including a computer and a printer which are connected together through a network, so-called secure printing is known as a technique to ensure security when image data transmitted from the computer are printed out by the printer. In general secure printing, image data and a password set thereon are first transmitted from a computer to a printer. After a user has entered a password through an operation section of the printer, the image data are printed out when the password has coincided with the transmitted password. However, in such an image forming system, the image data cannot be printed out immediately when the printer to which the user has sent the image data is occupied by another user or faulty.
In contrast, in the image forming system described in JP-A-2003-131842, when secure printing is performed, the computer first sends the image data to all printers (virtual printers) connected to the network. A printer to which a user has entered a valid password prints out the image data. As a result, the user can print out image data from an arbitrary printer.